Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 33

Liczba wyników na stronie
first rewind previous Strona / 2 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  complex
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 2 next fast forward last
EN
Nine new vanadium complexes, with tridentate Schiff base ligand based on 3,5-di-tertbutyl-2-hydroxybenzaldehyde and different hydrazides, are described and characterized. The X-ray crystal structure of complex 8 shows distorted octahedral geometry of vanadium, with ONO ligand in equatorial position. The tridentate Schiff base ligand forms six membered and five-membered chelate rings at the V(V) acceptor center, with the corresponding bite angles being 82.97(9)˚ and 74.48(9)˚. The molecules are gathered by means of intermolecular OH...N hydrogen bond and layered by π...π interactions involving the pyridine and phenolate rings. Such interactions expand the structure along the crystallographic a axis. The complexes were characterized by the elemental analyses, IR, UV-Vis, EPR spectroscopy, cyclic voltammetry, thermogravimetry and magnetic susceptibility measurements. The stabilization role of co-ligands is discussed. The cytotoxicity versus HepG2 hepatocytes and inhibition of human recombinant PTP1B was studied.
EN
The synthesis and physicochemical properties of three new complexes of vanadium at +5, +4 and +3 oxidation state are described and discussed. The octahedral surrounding of vanadium for V(III) complexes of [V(L1)(HL1)] general formula is filled with two ONO tridentate ligand L, for V(IV) one ONO ligand L, oxido ligand and 1,10-phenanthroline (phen) as a co-ligand are presented in complexes of [VO(L2)(phen)]. For V(V) the complexes of [VO2(L1)(solv)] type were formed. As ligands, the H2L Schiff bases were formed in reaction between 5-hydroxysalcylaldehyde and phenylacetic hydrazide (H2L1) and 3,5- dichlorosalicyaldehyde and 4-hydroxybenzhydrazide (L2). The magnetic moment measurements, in 8 year period, show, that V(III) complexes slowly oxidise to V(IV) with preservation of the nonoxido character of the complexes, while V(IV) complexes were found to be stable. The TG and SDTA measurements indicate, that thermal stability depends mainly on the oxidation state of vanadium. The less thermally stable are the V(V) complexes, while V(IV) and V(III) are stable up to ca. 200oC. In solution, at pH 2 (similar to that in human digestion system), again the V(IV) are the most stable, only at pH 7.0 V(III) complexes had higher stability. The most stable, thus best for pharmaceutical use, are V(IV) complexes.
EN
The oxidovanadium(V) Schiff base complex of formula [VO(L)(EtO)(EtOH)] (where H2L = Schiff base ligand derived from 5-methoxysalicylaldehyde and phenylacetic hydrazide) was synthesized and described. Complex crystalizes in triclinic P-1 space group. Octahedral geometry of the vanadium(V) centre is filed with oxido, ONO L2- ligand and two solvent molecules both in ethoxo and as neutral ethanol form. The complex is neutral, with 5- and 6-memebered ring formed by ONO ligand coordinated in octahedral plane with oxido and EtOH ligands in vertical positions. Two isomers are present in the unit cell, with different position of 5-membered ring versus vertical plane. The elemental analysis, magnetic susceptibility, thermogravimetry and spectroscopy (IR, UV-Vis) measurements were measured and are discussed. The cyclic voltammetry measurements show irreversible processes for vanadium(IV/V) redox system. Thermal stability both in a solid state (TG and SDTA measurements) as well as in solutions (at pH 7.0 and 2.0, studied by UV-Vis spectroscopy) is discussed.
EN
The synthesis and physicochemical properties of new vanadium(IV) complex of formula [VO(L)(phen)] is described. The L denotes ONO tridentate Schiff base derived from 2,3-dihydroxybenzaldehyde and phenylacetic hydrazide, while phen = 1,10-phenanthroline used as a co-ligand to stabilize the V(IV) oxidation state. The single crystal X-Ray crystal structure indicates on octahedral geometry of vanadium centre, with 1,10-phenanthroline nitrogen trans to the V=O bond. The complex crystalizes in a monoclinic P21/c space group, very unusual is that only one isomer is present in the crystal structure. The structure is stabilized by very weak hydrogen bonds and H··π and π···π interactions. The phenyl ring of hydrazide is strongly curved from ONO ligand plane by 70.95˚. The spectroscopic characterization (IR, UV-Vis) as well as the cyclic voltammetry measurements are presented and discussed
EN
The synthesis and physicochemical properties of vanadium(III,IV,V) complexes with Schiff base ligands based on 3,5-dibromo-4-methoxy-salicylaldehyde and phenylacetic hydrazide (H2L1), 5-chlorosalicylaldehyde and 4-hydroxybenzhydrazide (H2L2) and 5- chlorosalicylaldehyde and 2-hydroxybenzhydrazide (H2L3) were presented. The formulas of the complexes {[V(L1)(HL2)]·EtOH (1), [VO(L2)(phen)]·2H2O (2) and [VO(L3)(EtO)] (3)} were proposed based on the elemental analysis, IR and UV-Vis spectra. Additionally, the IR and UV-Vis spectra (in solvents as well as in a solid state) have been discussed from the vanadium oxidation state point of view. The single crystal structure of 3 shows triclinic, P-1 space group, structure is stabilized by hydrogen bonds and strong π-π stacking interactions. The oxidation state of the metal centre was also confirmed by the magnetic susceptibility measurements. The stability of the complexes was measured in pH = 7.00 and in pH = 2.00 which allows to evaluate the use of these compounds as insulin mimetic compounds.
EN
The problem of reduction of linear electrical circuits with complex eigenvalues to linear electrical circuits with real eigenvalues is analyzed. Methods for finding the transformation matrix are presented. Considerations are illustrated by numerical examples.
EN
This paper reports on studies conducted during 2005–2006 years in the ecosystem of the Solina-Myczkowce mountain complex of mesotrophic reservoirs on the San River, SE Poland. The goal of the present study has been to analyse the functioning of the reservoirs as a dissolved silicon sink especially whether silicon assumes a limiting role where the biological productivity of reservoirs waters is concerned. Silicon is one of the biosphere’s most abundant elements, and one that – in the form of dissolved silica – serves as a very important nutrient playing a major role in the functioning of marine, coastal and inland waters. Investigations indicate that reservoirs are major sinks for the dissolved silica in a river system and that unfavorable changes in water chemistry downstream may ensue where (as is usually the case), the water discharged from a reservoir is poorer in Si than that supplied to it. The noted Si depletion in both the analysed reservoirs influenced growth of non-siliceous algae expressed in terms of chl a. Siliceous algal growth is usually observed there during spring. I suppose that the first chl a maximum in the case of the Solina Reservoir, and the only maximum in the Myczkowce Reservoir, result from the growth of both siliceous and green algae. The next increase in chl a – observed only in the Solina Reservoir – may result from the presence of the cyanobacteria often observed in warm lakes at the end of summer. Their absence from Myczkowce reflects the low temperature of that reservoir’s water, this being supplied from the hypolimnion of the upper one. These observations are confirmed in relationships between mean measured concentrations of Si and mean concentrations of chl a in the euphotic zone of the two reservoirs. Observed summer depletion of the silicate accelerates the growth of phytoplankton exponentially, especially in the case of the upper reservoir.
8
Content available remote Non-pulsed mode of supply in a three-phase system at asymmetrical voltage
EN
Two orthogonal decompositions of a total three-phase current are considered for a three-phase system with asymmetric sinusoidal voltage at the connection point of asymmetrical loading. In the first one the total current is represented as an orthogonal sum of balanced and nonbalanced current components, the balanced component containing Fryze's active current (active power). In the second decomposition the total current is represented as an orthogonal sum of pulsed and non-pulsed current components. Both decompositions are used to create the optimal mode of supply with a constant instantaneous power at asymmetrical voltage.
PL
Analizowano ortogonalna dekompozycję prądów trójfazowych w systemie z napięciem asymetrycznym dołączonym do asymetrycznego obciążenia. Prąd całkowity jest sumą składowej zrównoważonej i niezrównoważonej.
EN
The complexes of poly(ethyl methacrylate-co-N-vinyl-2-pyrrolidone) (P(EMA-co-VP)) gel with poly- (ethylene glycol) (PEG) stabilized by the hydrogen bonds were prepared. It was found that both the concentration and the molecular weight of PEG have a strong effect on the P(EMA-co-VP) gel. When PEG was introduced into the P(EMA-co-VP) gel, the glass transition temperatures (Tg) of the complexes decreases with the decreasing of PEG molecular weight. In such a system, the maximum molecular weight of PEG required for the complex formation is no more than 2000, and P(EMA-co-VP)/PEG complexes are a homogeneous amorphous phase, which was studied by FTIR, XRD, TEM, and DSC.
PL
Wobec limitów na produkcję żywności nałożonych na Polskę przez Unię Europejską, wykorzystanie płodów rolnych do celów inżynierii środowiska może być korzystne dla krajowego rolnictwa i gałęzi przemysłu współpracujących z rolnictwem. Obecny stan techniki i znane technologie pozwalają otrzymać z roślin i materiału roślinnego zawierającego sacharydy i polisacharydy szereg podstawowych materiałów dla przemysłu chemicznego. Cennym surowcem mogą być też hemicelulozy i celuloza oraz rośliny zawierające te polisacharydy. Efektem poznawczym są badania dotyczące wykorzystania słomy różnego pochodzenia botanicznego (jęczmienia, owsa, pszenicy, pszenżyta, żyta) jako źródła biopaliw poprzez degradację do gazu syntezowego i karbonizatu. Zostały przeprowadzone badania przy użyciu analizy termicznej DSC/TG oraz TGA/SDTA/QMS mające na celu dobór najlepszych warunków procesu otrzymywania karbonizatów oraz składu jakościowego wydzielanych gazów, a także badania przy użyciu dyfraktometru rentgenowskiego mające na celu określenie budowy sfery koordynacyjnej wokół dodanego jonu metalu. Produkty otrzymane w wyniku termicznego rozkładu biomasy i ich wykorzystanie jako kolektorów jonów metali, dodatków do płuczek wiertniczych oraz w produkcji biopaliw może spowodować poprawę bezpieczeństwa energetycznego oraz poprawę bezpieczeństwa środowiska naturalnego.
EN
The interaction of polysaccharides and cereal grains with transition metal ions is of a biochemical importance, mostly due to the presence of those complexes in biological systems. Metal polysaccharide chemistry plays a crucial role in crosslinking of various biomolecules, and formed polysaccharide/metal complexes are promising for various application, e.g. as drilling muds, heavy metal collectors and material for production of carbonizate and gaseous substances allowing preparation of second generation biofuels. In the study of cereal/metal complexes, the thermogravimetric measurements were also made in order to explain the influence of metal salts on thermal decomposition of barley, oat, rye, triticale, and wheat grains in aspect of their applications for biofuels production. In investigation of polysaccharide/metal complexes, mainly concerning their conductivity as well as thermal stability and rheological properties, a special attention was paid to interactions of transition metal salts with potato, amarantus and cassava starch, potato amylose and potato as well as corn amylopectin.
EN
The optimal methodology to prepare the novel modified enzyme, polymer-enzyme complex, was developed to give a high catalytic activity in aqueous solution. The non-covalent complexes of two different enzymes (horseradish peroxidase and glucose oxidase) were prepared with various molar ratios (nD/nE 0,05; 0,1; 1; 5; 10; 15; 20) by using 75kDa dextran. The thermal stabilities of the obtained complexes were evaluated with the activities determined at different temperatures (25, 30, 35, 40, 50, 60, 70, 80°C) applying 60 minutes incubation time for pH 7. The complexes with the molar ratio nD/nHRP: 10 and nD/nGOD: 5 showed the highest thermal stability. Its activity was very high (ca. 1,5-fold higher activity than pure enzyme for HRP-dextran complexes) and almost the same between applying one hour incubation time and without incubation, and could also be measured at high temperatures (70, 80 °C). We finally succeeded in preparing dextran-enzyme complexes which showed higher activity than pure enzyme in aqueos solution at all temperatures for pH 7. In addition, the mentioned complexes at pH 7 had very long storage lifetime compared to purified enzyme at +4 °C; which is considered as a good feature for the usage in practice.
EN
The proposed methodology is worked out for the aims of oil and gas geology and can be used at investigation of terrigenous, terrigenous-carbonate and carbonate sections. It can also be used at prospecting and exploration of coal, ore, diamond deposits and underground water, as well as at the solving the tasks that need the detailed knowledge of the section structure (gas storages, slide dangerous zones etc.). The methodology includes the new methods and techniques of processing and interpretation of geophysical data. It is realized as a programme-methodical complex (PMC) "Seismocyclit" and "AFCM" - amplitude-frequency characteristic of medium, computed according to the noise constituent of wave field. It is based on the theory of sedimentary cyclicity - lithology (the teaching about rock-formations associations) and on the assumption of discompaction and compaction zones existence (the zones of reservoirs and cap rocks development). The uniting of the known geophysical methods and techniques, which were tested by time with the worked out by us techniques of processing and interpretation have led to creation of the new instrument for geological investigations. The advantages of our methodology in comparison with the commonly used methods consist in the possibility of obtaining the new qualitative data as to geological structure of the studied areas, which permit to carry out the forecast of hydrocarbons pools.
PL
Zaproponowana metodologia została opracowana na potrzeby geologii naftowej i gazowej i może być wykorzystana do badania części terygenicznych, terygeniczno-węglanowych i węglanowych. Może ona być także wykorzystana do poszukiwań za węglem, rudami, złożami diamentów i wód gruntowych, jak również przy rozwiązywaniu zadań wymagających dogłębnej wiedzy na temat struktury danej części (zbiorniki gazu, niebezpieczne strefy osuwisk itp.). Zaprezentowana metodologia obejmuje nowe metody i techniki przetwarzania i interpretacji danych geofizycznych. W praktyce przyjmuje to postać kompleksu programowo-metodycznego "Seismocyclit" oraz charakterystyki amplitudowo-częstotliwościowej ośrodka "AFCM", obliczonej zgodnie ze składową hałasu pola fal. Podstawą jest teoria sedymentacyjnej cykliczności litologicznej (nauki o związkach skał i formacji) oraz założenie istnienia stref dekompakcji i kompakcji (stref rozwoju zbiornika i nadkładu skalnego). Połączenie znanych metod i technik geofizycznych, które zostały sprawdzone za pomocą opracowanych przez autorów technik przetwarzania i interpretacji doprowadziło do stworzenia nowego instrumentu do badań geologicznych. W porównaniu z innymi, powszechnie stosowanymi metodami, przedstawiona autorska metoda ma zaletę polegającą na możliwości otrzymywania nowych danych jakościowych na temat struktury geologicznej badanych obszarów, umożliwiających wykonanie prognoz dotyczących złóż węglowodorów.
EN
A tripodal ligand, 1,1,1-tris-[1c-(2c-oxa-4c-oxo-5c-aza-5cbisphenyl)hexyl]pro pane (L), pyridine-N-oxide and their ternary complexes with rare earth nitrates have been synthesized. These new complexes with the general formula of Ln2źLźPyNOź(NO3)6źnH2O (where Ln = La, Nd, Tb, n = 3; Ce, n = 4; Pr, n = 1; Eu, n = 2) were characterized by elemental analysis, IR spectra, 1H NMR, mass spectrum, thermal analysis and molar conductiviity. All the complexes are stable in air. The results show that the lanthanide ions in each complex are coordinated by ox ygen atoms of the ligand, PyNO and the nitrates. The fluorescent properties of the Eu(III) and Tb(III) complexes in CH3OH were investigated. Tentative structures for the complexes have been proposed.
EN
The iodine-azide reaction selectively induced by sulfur(II) compounds has been used for the investigation of metai complexes with 2-mercaptopyrimidine and its ten homologues. Substitution of mercaptopirymidines ligands with azide ions at a milimolar level has been investigated. The studied complexes were arranged in the inertness series. The time of complex formation and their composition have been established.
PL
Reakcję jodo-azydkową indukowaną selektywnie przez związki siarki dwuwartościowej zastosowano do badania kompleksów metali z 2-merkaptopirymidyną i jej dziesięcioma homologami. Reakcję wymiany ligandów merkaptopirymidynowych na jony azydkowe badano na poziomie milimoli, podano szeregi bierności kompleksów oraz skład i czas ich tworzenia.
15
EN
Investigation of interactions between ketoprofen and N-acetyl-L-tyrosine ethyl ester are reported. Formation of the complex was studied using fluorescence spectroscopy and computer modeling. The fluorescence decay time let us determine the quenching mechanism and thus conclude that the complex is formed in the ground-state. The complex structure was than optimised using the computer programme proving the formation of two unequal hydrogen bonds between ketoprofen and tyrosine molecules.
PL
W pracy opisano badania oddziaływań pomiędzy ketoprofenem a N-acetylowym estrem etylowym L-tyrozymy. Tworzenie kompleksu badano metodami fluorescencyjnymi oraz poprzez modelowanie molekularne. Pomiar czasu zaniku fluorescencji umożliwia określenie mechanizmu wygaszania fluorescencji kompleksu, co z kolei pozwala wnioskować, że kompleks pomiędzy tyrozyną a ketoprofenem tworzy się w stanie podstawowym. Komputerowa optymalizacja struktury tworzonego kompleksu wskazuje na istnienie dwóch niejednakowych mocy wiązań wodorowych.
EN
The complex formation of Cu2+ with some recently synthesized methyl-substituted ethylenediimines in binary dimethylformamide-ethanol mixtures was studied by differential pulse voltammetry. The stoichiometry and the stability of the complexes were determined by monitoring the increasing complex peak current against the ligand concentration using nonlinear least squares-Excel solver. In all studied cases, it was found that the stability of the resulting 1:1 complex decreases by increasing the amount of ethanol in the binary mixtures. The observed stability order is discussed in terms of the solvent binary mixtures and the nature of the substituted ethylenediimine structure.
PL
W pracy określono zależności plonowania pszenżyta ozimego od sumy i rozkładu opadów w wybranych okresach wzrostu i rozwoju oraz w całym okresie wegetacji, w południowej części Polski, na glebach pszennych i żytnich. Na podstawie 1413 danych z lat 1981-1996 pochodzących z 12 stacji doświadczalnych przeprowadzono badania, które umożliwiły określenie wpływu wysokości i rozkładu opadów na wielkość plonu pszenżyta ozimego. Jakość gleby istotnie wpływała na plony pszenżyta ozimego. Najwyższe plony na kompleksach pszennych (ok. 7,0 t·ha-¹) wystąpiły, gdy suma opadów wynosiła 180-220 mm, liczba dni z opadem ≤ 5 mm - 35-45, a ogólna liczba dni z opadem - 50-60. Na kompleksach żytnich największy plon (6,5 t·ha-¹) otrzymano, gdy suma opadów wynosiła ok. 220-260 mm, liczba dni z opadem ≤ 5 mm była większa niż 50, a ogólna liczba dni z opadem - większa niż 60.
EN
The paper presents dependence of winter triticale yielding on the sum and distribution of rainfall in particular growth stages and throughout the vegetation season in the southern part of Poland on wheat and rye soils. The study was based on 1413 results of experiments carried out at 12 experimental stations in the years 1981-1996. Soil quality had a significant effect on winter triticale yielding. The highest yields of ca. 7.0 t·ha-¹ on wheat complexes were obtained under the following conditions: rainfall 180-220 mm, the number of days with rainfall ≤ 5 mm - 35-45 days and the overall number of days with rainfall 50-60 days. The respective figures for rye complexes (yield 6.5 t·ha-¹) were: 220-260 mm, over 50 days and over 60 days.
PL
W pracy określono zależności plonowania pszenżyta ozimego od sumy i rozkładu opadów w następujących okresach rozwojowych: wiosenny początek wegetacji - strzelanie w źdźbło, strzelanie w źdźbło - dojrzałość woskowa oraz w całym okresie wegetacji na glebach pszennych i żytnich w środkowej części Polski. Na podstawie 2437 danych z 19 stacji doświadczalnych z lat 1981-1996 opracowano modele plonowania. Przeprowadzone badania umożliwiły określenie, które z badanych parametrów i w jakich okresach mają istotny wpływ na wielkość plonu ziarna pszenżyta ozimego. Największe plony na kompleksach pszennych (ok. 7,3 t·ha-¹) wystąpiły, gdy opady wyniosły 200-240 mm. Liczba dni z opadem ≤ 5 mm i ogólna liczba dni z opadem nie wpływały wyraźnie na plon. Na kompleksach żytnich największy plon (6,5 t·ha-¹) otrzymano, gdy suma opadów wynosiła ok. 200-260 mm, liczba dni z opadem ≤ 5 mm była większa niż 45, a ogólna liczba dni z opadem - większa niż 60.
EN
The study presents dependence of winter triticale yielding on the sum and distribution of rainfalls in the growth stages: beginning of vegetation - shooting, shooting - dough maturity and in the whole vegetation season. Winter triticale was grown on wheat and rye soils in the middle part of Poland. Based on 2437 one-year experiments from 19 experimental stations over 1981-1996, a model of yielding has been elaborated. The study allowed determining which of the studied parameters and when exerts an essential impact on the yield of winter triticale. The largest yields of ca. 7.3 t·ha-¹ was obtained on wheat complexes when rainfall was 200-240 mm. The number of days with precipitation ≤ 5 mm and the total number of days with rainfall did not significantly correlate with the yield. The largest yield (6.5 t·ha-¹) on rye complexes was obtained at total rainfall ca. 200-260 mm, the number of days with rainfall ≤ 5 mm over 45 days and overall number of days with rainfall greater than 60 days.
EN
The thermal decomposition of tin(II), lead(II), cadmium(II) and mercury(II) metal-alginate complexes has been studied using thermogravimetry (TG) and differential thermogravimetry (DTG) measurements. The TG curves showed three stages of weight loss, the DTG curves indicated the presence of a series of thermal stages associated with the TG curves. Dehydration of the coordinated water molecules occurred in the first stage, followed by decomposition of the dehydrated complexes in the next two stages. Thermal stability of these complexes in terms of the strength of chelation and coordination geometry is discussed.
EN
Some new tin(II) complexes have been synthesized by the reactions of tin(II) methoxide with nitrogen donor ligands. The ligands used in these studies are condensation products of heterocyclic aldehydes/ketones and sulpha drugs. Their structures have been confirmed on the basis of elemental analyses, ultraviolet, infrared and multinuclear magnetic resonance (1H, (13)C and (119)Sn) spectral studies. The bivalent nature and their square pyramidal geometry around tin(II) have been deduced on the basis of 119Sn Mossbauer spectral data. Monomeric and non-electrolytic nature of these complexes have been confirmed by molecular weight determinations and conductance measurements.
first rewind previous Strona / 2 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.